Attention and learning problems among children exposed to opiates in utero
have been previously reported but are difficult to interpret due to imprecise measurement
and inadequate control of postnatal factors. In this study, we used a behavior-based measure
of attention (continuous-performance tasks) and a physiological index of sustained attention
(cardiac vagal tone) to measure more precisely the process of sustained attention. Boys,
aged 7 to 12, exposed to opiates in utero, were compared to boys whose mothers began using
illicit substances after the child's birth (environmental controls), and boys whose mothers
were non-drug users. This three-group design was intended to isolate in utero effects from
postnatal environmental influences. Vagal tone, a measure of heart-rate variability sensitive
to vagal influences on the heart, was measured pre- and postbaseline and during the three
tasks of the Gordon Diagnostic System (Delay, Vigilance, and Distractibility). Vagal tone
has been found to be sensitive to changes in environmental demand for sustained attention in
infants, school-age children, and adults. Results indicated that when distractors were added
to the vigilance task (Distractibility task), opiate-exposed boys failed to suppress vagal tone
compared to both control groups. However, both the opiate-exposed boys and the environmental
controls made fewer correct responses than non-drug-exposed controls on this task.
These results indicate that normal physiological responses to increased attentional demand
may be impaired in boys exposed in utero to opiates in this age range. However, the poor
Distractibility scores of both the opiate-exposed and environmental controls suggests an
important role of environmental influences on attentional performance.